Silicon carbide furnaces and plants

ABSTRACT

A SILICON CARBIDE MANUFACTURING PLANT FOR MANUFACTURING SILICON CARBIDE IN A MOVABLE FURNACE AT ONE AREA, DISCHARGING THE FURNACE IN A SECOND AREA AND LOADING IN A THIRD AREA. AN ELECTRICAL POWER SOURCE IS PROVIDED HAVING A MAIN TRACKWAY ADJACENT THE POWER SOURCE WITH A FURNACE CAR MOVABLE TO AND FROM SAID POWER SOURCE AND REMOVABLY CONNECTED THERETO THROUGH ELECTRODES ON END PANELS ON THE CAR.

SILICON CARBIDE FURNACES AND PLANTS Original Filed Feb. 23, 1967 4 Sheeias-Sheet l @L SJ mm vw NN SQL 8J SWS cui Qw\ o,\\ IFIIIFL GNN Jan. 5,1971 w, r BOLKCQM EI'AL Re. 27,018

SILICON CARBIDE FURNACES AND PLANTS Original Filed Feb. .23, 1967 4Sheets-Sheet 2 INVENTORs WJLUH T/Kcol d LJ. ma," Kw# Jan. 5, w. T'BQLKCOM ETAL Re. SILICON CARBIDE FURNACES AND PLANTS Original Filed Feb.23, 1967 4 Sheets-Sheet 5 Jan. 5, 1971 w. 1'. B oLKcoM ETAL SILICONCARBIDE FURNACES AND PLANTS Original Filed Feb. 23, 1967 4 Sheets-Sheet4 n gm@ .------l------i-- vlllllll lllllllll IIIAIIIIIIII n \I-i--. l 1/f. /f f+ w f J J N w--- wm wm m J 2 rfllissi-; l I I I llllllllllli'lL27,018 SILICON CARBIDE FURNACES AND PLANTS Wilbur T. Bolkcom,Pittsburgh, Pa., and William E.

Knapp. Allison Park, Pa., (both American Metallurgical Products Co.,9800 McKnight Road, Pittsburgh, Pa. 15237) Original No. 3,432,605, datedMar. l1, 1969, Ser. No. 618,034, Feb. 23, 1967. Application for reissueNov. 20, 1969, Ser. No. 878,283

Int. Cl. Hb 3/02, 3/62 U.S. Cl. 13-20 14 Claims Matter enclosed in heavybrackets appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additionsmade by reissue.

ABSTRACT OF THE DISCLOSURE A silicon carbide manufacturing plant formanufacturing silicon carbide in a movable furnace at one area,discharging the furnace in a second area and loading in a third area. Anelectrical power source is provided having a main trackway adjacent thepower source with a furnace car movable to and from said power source ndremovably connected thereto through electrodes on end panels on the car.

This invention relates to silicon carbide furnaces and plants andparticularly to a silicon carbide furnace which can be fired in oneposition, removed to a second position for cooling and unloading and toa plant incorporating a plurality of such furnaces.

In the past silicon carbide has been manufactured in stationary electricfurnaces. Such stationary furnace installations usually require four tosix furnaces for each transformer in order to utilize the transformer toits maximum efficiency, with one furnace heating, one being unloaded,one loading, and the remainder cooling. This requires very large capitalinvestment in buildings and furnaces. The unloading of such furnaces isquite diflicult and tedious because of the adjacent hot furnaces andbecause of the necessity of using large amounts of hand labor to removethe silicon carbide from the furnace due to the proximity of theadjacent furnaces and the difficulty of using mechanical unloadingequipment in the restricted floor space available. This also requiresthat the furnaces be cooled in extraordinary long time before unloadingin order to get the temperature down to the point where the hand laborcan be effectively used. A further problem arises in the loading of suchfurnaces because of the adjacent other furnaces. This means lengthyconveyor belts from the mixing bins to the furnaces or overhead cranescarrying successive bucket loads to the furnace.

We have invented a silicon carbide furnace and plant which eliminatesthese problems and makes it possible to produce a given quantity ofsilicon carbide in a plant area less than 1/3 the size of that requiredby conventional methods.

Preferably we provide an electrical power source, a main trackwayadjacent said power source, a furnace bottom mounted on wheels on saidtrackway movable to andl away from said power source; said furnacebottom having a substantially fiat heat resistant surface, removablesides along each side of said surface and removable ends on saidsurface, said sides and ends defining a heating chamber, electrode meansin each of said ends, removable connections between said electrode endsand said power source, a transfer car movable transversely to the maintrackway and having a corresponding trackway adapted United StatesPatent O lCe to be aligned with the main trackway to receive the furnacebottom wheels and furnace whereby said furnace may be moved transverselyto said main trackway, a service area spaced from said main trackwuy bysaid transfer car, secondary trackways in said service area receivingsaid furnace from said transfer car, loading means at said service areaadapted to load said furnace and a cooling and unloading section in saidservice area spaced from the loading means. Preferably the loading meansis a gravity discharge hopper or the like located over a trackwayadapted to receive a furnace to be loaded from the transfer car. Otherloading device and conveying equipment, may of course, be used. Theremovable ends of said furnace are preferably provided with coolingmeans removably connected to a source of coolant adjacent the powersource whereby the electrodes in the ends can be cooled.

In a preferred embodiment, the sides are a plurality of side-by-sidecast iron panels lined with refractory and removed and replaced bycrane, loader or similar lifting device.

In the foregoing general description of our invention we have set outcertain objects, purposes and advantages of our invention. Otherobjects, purposes and advantages will be apparent from a considerationof the following description and the accompanying drawings in which:

FIG. 1 is a plan view of a silicon carbide plant iioor according to ourinvention;

FIG. 2 is a side elevation of a silicon carbide furnace according to ourinvention;

FIG. 3 is a top plan View of the furnace of FIG. 2;

FIG. 4 is a section on the line lV-IV of FIG. 2;

FIG. 5 is a section on the line V-V of FIG. 2; and

FIG. 6 is an enlarged fragment elevation of the furnace end and clampingdevice.

Referring to the drawings we have illustrated in FIG. l a furnacebuilding floor 10 having three transformer units 11, 12, and 13.Adjacent each transformer unit is a pair of trackways 14a-14h, 15a-15b,and 116a16b each made up of spaced rails. A transfer pit 17 is providedat the end of the trackways remote from transformer units and extendingtransverse to the length of the trackways. Rails 18, 19, 20 and 21 areprovided in the pit to carry a transfer car 22 mounted on wheels 23riding on rails 18, 19, 20 and 21. A trackway 24 is mounted on thetransfer car 22 level with the plane of trackways 14a-14h, 15a-15b, and16a-16h and adapted to be selectively aligned with any one of saidtrackways by movement of the transfer car. The transfer car is driven byany of various wellknown drive means from end to end of pit 17 to aligntrackway 24 with the furnace lioor trackways. A service area 25 isprovided adjacent pit 17 on the side opposite furnace floor 10. Theservice area is provided with a stripping floor 26 having a trackway 27on the same plane as trackways 14a-14b, 15a-15b, and 16a-16h. A loadingiioor 28 is also provided in service area 25 and it too is provided witha trackway 29 on the same plane as trackways 14a-14b, 15a-15b, and116a-16b. Both trackways 27 and 29 terminate at pit 17 so that trackway24 on transfer car 22 may be aligned with them. An overhead loadinghopper (not shown) is provided adjacent trackway 29 to discharge bygravity over trackway 29.

A furnace car having a furnace bottom 30 mounted on wheels 31 is adaptedto move on wheels 31 on the several trackways 14a-14b, 15a-15b, 16a-16b,24, 27 and 29. A heat resistant surface 32 is provided on the bottom 30.This surface may be of cast concrete, brick or any of various well-knownrefractory materials. Identical end panels 33 are removably mounted oneach end of the bottom 30. These end panels are made up of a steel frame34 carrying a cast concrete end member 35 having a 3 refractory face 36of high temperature brick or like refractory material and provided withan opening 37 receiving an electrode 38.

A plurality of removable side panels 40 extend along each side of thebottom between the two end panels 33 to form a trough-like receptacle.The side panels 40 are made up of an inclined bottom plate 41 andvertical side plate 42 of cast iron or like material carried by asupporting frame 43. The bottom plate 41 and side plate 42 are linedwith refractory brick 44. The two bottom plates 41 from opposite sidesmeet generally at the center line of bottom surface 32 to form agenerally U-shaped bottom on the receptacle. The electrodes 38 areconnected to transformers 11, 12 or 13 by means of cables 50 and busbars50a, each busbar serving a pair of furnaces, and removable electrodeclamps 51. The clamps S1 are preferably water cooled by water introducedinto passages in the clamps by water line 52.

The operation of the plant and furnace of our invention is as follows.The end panels 33 with electrodes 38 mounted in openings 37 are placedon bottom surface 32. The side panels 40 are then placed on bottomsurface 32 to complete the furnace. The end panels and side panels maybe placed in position by a high-lift, overhead crane, traveling oorcrane or like device. This work is done on the trackway 27 on thestripping door. The furnace car is then moved from trackway 27 ontotrackway 2,4 on transfer car 22 by means of a high-lift, a winch andcable or any of well known means. The transfer car 22 is then moved totrackway 29 where the furnace car is moved onto trackway 29 and loadedby gravity. The furnace charge is a conventional charge for the Achesonprocess, i.e., silica and carbon around a carbon electrode core. In themeantime a furnace car ready for stripping may be moved into thestripping area as described hereafter. The furnace car is loaded fromthe hopper previously described or by some other conventional means andis then returned to the transfer car which is moved to one of trackways14a-14b, 15a-15b, or 16a-1Gb. The loaded car is moved onto one of thefurnace floor trackways to a position adjacent one of the transformers11, 12 and 13. Clamps 51 are applied to electrodes 38 which are incontact with carbon electrode cores 60 of the furnace charge. Theelectrical current is applied from the transformer along with watercoolant for the clamp. When the charge has been heated to the requiredtemperature and time for conventional Acheson process silicon carbide,the electrical current is stopped and the clamps are removed fromelectrodes 38. The clamps are then moved to a furnace car on the nextadjacent track of a pair of example 14a- 14b. This adjacent car is thenheated while the just completed car cools. Prior to completion of theheating process on the second adjacent car, the rst car is removed frornthe furnace floor trackway onto transfer car 22 and from there totrackway 27 on the stripping floor and a newly loaded car position inits place ready to receive the clamps 51 on completion of the secondcar.

When the furnace car is moved onto trackway 27, the side panels 40 arelifted off the bottom surface and the contents of the car pushed ofibottom surface 32 onto the stripping floor 26 by means of a high-lift orlike device and moved to a storage or loading area. The side panels 40are replaced and the car is ready to repeat the cycle.

The advantage in time saved and labor saved as well as capitalinvestment in buildings and fixed furnaces by our invention will beobvious to persons familiar with conventional silicon carbide plants.Hand labor is substantially eliminated in the plant of our inventionwhereas it makes up a very large part of the conventional practices.Much time is saved because unloading can be done at much highertemperatures by the simple expedient of pushing the completed charge offthe flat bottom car surface rather than digging it piece by piece fromthe fixed furnaces of the prior art and loading it in the restrictedareas between such furnaces.

While we have illustrated and described certain preferred embodimentsand practices of our invention it will be understood that this inventionmay be otherwise embodied within the scope of the following claims.

We claim:

1. A silicon carbide manufacturing plant comprising an electrical powersource, a main trackway adjacent said power source, a furnace carmovable on said trackway to and from said power source, a refractorybottom on said car, removable side and end panels on said refractorybottom of said furnace car, said side and end panels beinginterconnected to form a heating chamber on said car, electrode means ineach end panel, removable connections between said power source andelectrode means, a transfer car movable on a trackway extendingtransversely to the main trackway, said transfer car carrying a trackwaycorresponding to said main trackway and alignable with the main trackwayreceiving the furnace car therefrom, a service area opposite the maintrackway and spaced from said main trackway by said transfer car, asecondary trackway on said service area receiving said furnace car fromsaid transfer car trackways, loading means in the service area forloading said heating chamber while on said secondary trackway and anunloading section in said service area spaced from the loading means andreceiving a completed furnace charge from said furnace car.

2. A silicon carbide manufacturing plant as claimed in claim whereincooling means are provided on each electrode.

3. A silicon carbide manufacturing plant as claimed in claim 1 whereinthe loading means includes an overhead receptacle above a portion ofsaid secondary trackway.

4. A silicon carbide manufacturing plant as claimed in claim 1 wherein apair of trackways are provided adjacent each power source, each trackwayreceiving a furnace car.

5. A silicon carbide manufacturing plant as claimed in claim 1 whereinsaid transfer car is movable ori tracks in a pit transverse to the maintrackway. 6. A silicon carbide manufacturing plant as claimed in claim 1wherein the side panels include an inclined lower portion terminatingadjacent the center line of the car.

7.. A silicon carbide manufacturing plant as claimed in claim l havingclamp means removable engaging said electrode means in each end panel,connections between saidlclamp means and said source of electricalpower, cooling means on said clamp means, a source of coolant, andconnections from said source of coolant to said cooling means.

i 8. A silicon carbide manufacturing plant as claimed in claim 7 whereinthe cooling means are coolant passages within the clamp means.

9. in a silicon carbide manufacturing plant having an electrical powersource, arid a main trackway adjacent said power source, the improvementcomprising a furnace car adapted to move on said trackway to and fromsaid power source, a refractory bottom on said car, removable side andend panels on said refractory bottom of said furnace car, said side andend panels being interconnected to form a heating chamber on said car,electrode means in each end panel, removable connections between saidpower source and electrode means, a transverse trackway intersectingsaid main trackway at a level below the main trackway and carrying amovable transfer car having a trackway alignable with the main trackway,a service area spaced from said main trackway by a transfer car, asecondary trackway in said service area receiving said furnace car fromsaid transfer car loading means in the service area adapted to load saidheating chamber while on said secondary trackway and an unloadingsection in said service area spaced from the loading means and receivinga completed furnace charge from said furnace Cur- 10. In a siliconcarbide manufacturing plant as claimed in claim 9 wherein the electrodeconnections are provided with cooling means.

1I. A silicon carbide manufacturing plant comprising an electrical powersource, a main trackway area adjacent said electrical power source, aplurality of spaced apart rst trackways on said main trackway area, afurnace car movable on each said track to and from said power source, arefractory bottom on each such car, removable side panels on saidrefractory bottom of said furnace car, end panels on said refractorybottom, said side and end panels being interconnected to form a heatingchamber' on said car, electrode means in each end panel, removableconnections between sain' power source and the electrode means, aservice area spaced from said main trackway area, second trackway onsaid service area on which said furnace cars are movable, transfer meansbetween the first trackway and the second trackway selectivelydelivering a furnace car from one to the other, loading means in theservice area for loading said heating chamber while on said secondtrackway and an unloading section in said service area spaced from theloading means and receiving a completed furnace charge from said furnacecar.

l2. A silicon carbide manufacturing plant comprising an electrical powersource, a main traclfway area adjacent the electrical power source, aplurality of spaced apart first trackways on the main trackway area, aplurality of furnace cars selectively movable on each said track to andfrom the power source, a refractory bottom on each said car, removableside panels on the refractory bottom of each furnace car, end panels onsaid refractory bottom, the side and end panels being interconnected toform a heating chamber on said car, electrode means in each end panel,removable connections between the power source and the electrode means,a service area spaced from the main trackway area, second trackway onthe service area on which the furnace cars are movable, a transfer areaintermediate the service area and the main trackway area and trackwaymeans in the transfer area for selectively connecting a track of themain trackway with a track of the service area whereby a furnace car maybe selectively routed for movement between any trackway on the maintrackway area and the trackway n the service area.

13. A silicon carbide manufacturing plant comprising an electrical powersource, a main trackway area adjacent said electrical power source, aplurality of spaced apart trackways on said main trackway area, afurnace car movable on each said trackway to and from said power source,a refractory bottom on each such car, removable side panels on saidrefractory bottom of said furnace car, end panels on said refractorybottom, said side and end panels being interconnected to form a heatingchamber on said car, electrode means in each end panel, removableconnections between said power source and the electrode means, a servicearea spaced from said main trackway area, trackway means on said servicearea on which said furnace cars are movable, transfer means between themain trackway area and the service area selectively delivering a furnacecar from a trackway on one to a trackway on the other, loading means inthe service area for loading said heating chamber while on a trackway onsaid service area and an unloading section in the service area spacedfrom the loading means and receiving a cornpleted furnace charge fromsaid furnace car.

14. A silicon carbide manufacturing plant comprising an electrical powersource, a main trackway area adjacent said electrical power source, aplurality of spaced apart trackways on said main trackway area, afurnace ear movable on each said trackway to and from said power source,a refractory bottom on each such car, removable side panels on saidrefractory bottom of said furnace car, end panels on said refractorybottom, said side and end panels being interconnected to form a heatingchamber on said car, electrode means in each end panel, removableconnections between said power source and the electrode means, a servicearea spaced from said main trackway area, trackway means on said servicearea on which said furnace cars are movable, translatory track meansbetween the main trackway area and the service area selectivelyconveying a furnace car from a trackway on one to a trackway on theother, loading means in the service area for loading7 said heatingchamber while on a trackway or said service area and an unloadingsection in the service area spaced from the loading means and receivinga completed furnace charge from said furnace car.

References Cited The following references, cited by the Examiner. are ofrecord in the patented file of this patent 0r the original patent.

UNITED STATES PATENTS 2,122,469 7/1938 Hitner 13-6 2,159,286 5/1939Moore 13-1 2,263,549 1l/l94l Peyches l3-6X 2,629,756 2/1953 Wilkins etal. 13-33X 2,694,097 1l/l954 Collin 13-34X 2,899,476 8/1959 Geli 13-63,155,758 ll/l964 Hill 13-25 3,305,619 2/1967 Molstedt et al. 13-6UXOTHER REFERENCES The Manufacture of Iron & Steel, voi. 3, Chapman &Hall, Ltd., London, 1960, pp. 83, 84.

BERNARD A. GILHEANY, Primary Examiner R. N, ENVALL, IR., AssistantExaminer U.S. Cl. X.R. 13-33 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Reissue No. 27,018 January 5, 1971 Dated Wilbur T. Bolkcom eta1.

Patent No.

Inventor(s) It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Column l, line 23, "nd" should read and Column 2, line 38, "lla" shouldread 16a line 57, "116e" should Signed and sealed this 25th day of May1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting OfficerCommissioner of Patents read 16a Column 4, line 29, after "claim" insertl FORM PO-105O (1G-69) UscoMM-DC GoLive-P69 U.S. GOVERNMENT PRINTINGOFFICE 1969 0-366-334

